1. Field of the Invention
The present invention relates generally to high-speed decoding of video data which has been encoded in accordance with an MPEG (Moving Picture Experts Group) international standard. In its particular aspects, the present invention is directed to a variable length decoder (VLD) and a MPEG decoder including such VLD for decoding MPEG data at high speeds such as needed for digital High Definition Television (HDTV).
2. Description of the Related Art
A high speed variable length decoder (VLD) suitable for MPEG video is described in U.S. Pat. No. 5,173,695 to Sun et al., issued Dec. 22, 1992, which is incorporated herein by reference. Such VLD is used for decoding variable length codes, in particular discrete cosine transform (DCT) coefficients organized in blocks within a macroblock, which coefficients have been entropy coded in value and run length.
The Grand Alliance (GA) standard for digital HDTV transmission over terrestrial and cable networks has recently been ratified (with some modifications) by the United States Federal Communications Commission (FCC) paving the way for the introduction of HDTV transmitter and receiver equipment in the very near future. This standard uses the ISO/IEC 13818-2 international standard (MPEG-2) for video compression. The (GA) HDTV standard because of higher resolution than standard definition (SD) video, requires higher data transmission rates, and consequently a faster decoding speed by a factor of six at the receiver, than needed for SD video.
Because of speed limitations of available technology, meeting these higher decoding speeds is a significant challenge. There is a need to provide for a decoder and decoder architecture which is optimized to handle the increased speed required by the GA HDTV standard.